The operating point of inductive loads can be set using a current which flows through the load. Inductive loads are, for example, electric motors in which the current flowing through the motor determines the speed of the motor, or solenoid valves in which the current flowing through the load determines a valve position of the valve. Such solenoid valves are used, for example, in automotive engineering in automatic transmissions and are used there to control a hydraulic pressure system.
A current through an inductive load can be regulated by applying a pulse-width-modulated voltage to the load. In this case, the pulse-width-modulated voltage is selected in such a manner that it alternately assumes a first signal level, at which a current through the load rises, and a second signal level, at which a current through the load falls. In this case, an oscillating current whose mean value can be regulated using the duty cycle of the pulse-width-modulated load flows through the load. In the case of a hysteresis regulating method, the pulse-width-modulated voltage is generated in such a manner that it respectively assumes the first signal level when the current has fallen to a lower hysteresis value and respectively assumes the second signal level when the current has risen to an upper hysteresis value. In this method, a frequency of the pulse-width-modulated voltage is dependent on the upper and lower hysteresis values as well as on the upper signal level of the pulse-width-modulated voltage and the inductance of the load.